Handle missing Python tests in CI

[Copilot]

The build (3.11) GitHub Actions job was failing in make test, not in dependency installation or static analysis. The test target invoked unittest with a literal tests/test_* module path, which breaks when the repository has no matching Python test files.

• Root cause

  • make test ran:

    uv run -m unittest tests/test_*

  • With no tests/test_*.py files present, unittest attempted to import tests/test_* as a module and failed with ModuleNotFoundError.

• Change

  • Updated the Makefile test target to detect whether any tests/test_*.py files exist before invoking Python tests.
  • When tests are present, it now uses unittest discover.
  • When no matching files exist, it exits cleanly with an explicit skip message.

• Behavior

  • Test execution remains unchanged for repositories that add tests/test_*.py files later.
  • Repositories without Python tests no longer fail CI on the test step.

@if [ -d tests ] && find tests -maxdepth 1 -type f -name 'test_*.py' -print -quit | grep -q .; then \
	${PYTHON} -m unittest discover -s tests -p 'test_*.py'; \
else \
	echo "No test files found in tests/; skipping test execution."; \
fi